I feel like every unit has its place, be it small or massive.
For Nod I (almost) never use: Cyborgs (too cost ineffective) , Buggies (max 1 on rare occasions for early scouting), TT's (outclassed by Titans & less useful + cost ineffective than rocket inf and attack cycles), and Stealth Tanks (Too expensive, only useful for harv killing and surprise attacks if opponent has no MSA).
For GDI I (almost) never use: Wolverines (same reason as Nod buggies), Hover MLRS (paper armor, too expensive, underwhelming attack power),